scholarly journals Comment on “Laboratory Measurement and Analysis of the Deteriorated Layer Permeability Coefficient of Soil–Cement Deteriorated in a Saline Environment”

Materials ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 196
Author(s):  
Rui Neves
Keyword(s):  
Mass Flow ◽  
Permeability Coefficient ◽  
Laboratory Measurement ◽  
Homogeneous Layer ◽  
Saline Environment ◽  
Future Studies ◽  
Soil Cement ◽  
Measurement And Analysis ◽  
The Right ◽  
Heterogeneous Layer

The derivation of a formula to compute the permeability coefficient in the commented paper assumes that the mass flow is homogeneous in a homogeneous layer of a specimen. This assumption is not correct when there is also, at least, one heterogeneous layer. Moreover, a mathematical lapse was found on one equation, that would prevent the right computation of the permeability coefficient, even if the assumption was correct. Although this does not invalidate the major conclusions of the study and has not an outstanding effect on the presented results, for the sake of rigor and sound background for future studies in this field, corrections to the published formulas and model are proposed.

scholarly journals Author Response to Comment on: Laboratory Measurement and Analysis of the Deteriorated Layer Permeability Coefficient of Soil-Cement Deteriorated in a Saline Environment

Materials ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 207
Author(s):  
Qing Jin ◽  
Xinzhuang Cui ◽  
Junwei Su ◽  
Tu Lu ◽  
Jieru Wang ◽  
...  
Keyword(s):  
Permeability Coefficient ◽  
Laboratory Measurement ◽  
Author Response ◽  
Saline Environment ◽  
Soil Cement ◽  
Measurement And Analysis

The authors thank Rui Neves for his discussions related to our work. Errors in the formula have been corrected as suggested by the discusser and data in the article have also been revised.

scholarly journals Laboratory Measurement and Analysis of the Deteriorated Layer Permeability Coefficient of Soil-Cement Deteriorated in a Saline Environment

Materials ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2245 ◽  
Author(s):  
Qing Jin ◽  
Xinzhuang Cui ◽  
Junwei Su ◽  
Tu Lu ◽  
Jieru Wang ◽  
...  
Keyword(s):  
Permeability Coefficient ◽  
Cement Content ◽  
Jiaozhou Bay ◽  
Logistic Function ◽  
Test Method ◽  
Saline Environment ◽  
Soil Cement ◽  
Dredger Fill ◽  
Cement Specimen ◽  
Curing Age

The deterioration of soil-cement in a saline environment leads to a reduction in strength and an increase in permeability. Effective methods of determining the deteriorated layer permeability coefficient of soil-cement are currently lacking. A laboratory test method for measuring the permeability coefficient of the deteriorated layer was proposed using the modified permeability coefficient testing apparatus. According to the proposed method, the permeability coefficient of the deteriorated layer could be obtained after testing the permeability coefficient of the soil-cement specimen in acuring room and testing the equivalent permeability coefficient and deterioration depth of the soil-cement specimen in a deteriorated environment. Using the marine dredger fill from Jiaozhou Bay as a case study, the deteriorated layer permeability coefficients of soil-cements with different cement contents were tested. It turned out that the permeability of the deteriorated layer increases with age. At the beginning of the curing age, higher cement content led to a smaller permeability coefficient of the deteriorated layer of soil-cement. As the curing age increased, the deteriorated layer permeability coefficient of the soil-cement with higher cement content increased. The evolution of the permeability coefficient of a deteriorated layer with age can be formulated as the Logistic function. This study provides support for anti-permeability designs of soil-cement structures in saline environments.

Simulation of Multi-Stage Compressor at Off-Design Conditions

2017 ◽  
Author(s):  
Feng Wang ◽  
Mauro Carnevale ◽  
Luca di Mare ◽  
Simon Gallimore
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Eddy Viscosity ◽  
Turbulence Models ◽  
Viscosity Model ◽  
Eddy Viscosity Model ◽  
Multi Stage ◽  
Pressure Profiles ◽  
Non Linear ◽  
The Right

Computational Fluid Dynamics (CFD) has been widely used for compressor design, yet the prediction of performance and stage matching for multi-stage, high-speed machines remain challenging. This paper presents the authors’ effort to improve the reliability of CFD in multistage compressor simulations. The endwall features (e.g. blade fillet and shape of the platform edge) are meshed with minimal approximations. Turbulence models with linear and non-linear eddy viscosity models are assessed. The non-linear eddy viscosity model predicts a higher production of turbulent kinetic energy in the passages, especially close to the endwall region. This results in a more accurate prediction of the choked mass flow and the shape of total pressure profiles close to the hub. The non-linear viscosity model generally shows an improvement on its linear counterparts based on the comparisons with the rig data. For geometrical details, truncated fillet leads to thicker boundary layer on the fillet and reduced mass flow and efficiency. Shroud cavities are found to be essential to predict the right blockage and the flow details close to the hub. At the part speed the computations without the shroud cavities fail to predict the major flow features in the passage and this leads to inaccurate predictions of massflow and shapes of the compressor characteristic. The paper demonstrates that an accurate representation of the endwall geometry and an effective turbulence model, together with a good quality and sufficiently refined grid result in a credible prediction of compressor matching and performance with steady state mixing planes.

scholarly journals Comparison of Different Empirical Correlations to Estimate Permeability Coefficient of Quaternary Danube Soils

2018 ◽  
Author(s):  
Miklós Pap ◽  
András Mahler
Keyword(s):  
Grain Size ◽  
Permeability Coefficient ◽  
Carpathian Basin ◽  
Laboratory Measurement ◽  
Granular Soils ◽  
Empirical Correlations ◽  
Soil Parameter ◽  
Measurement Results

Permeability coefficient is the most significant soil parameter in seepage calculations. It has been recognized that permeability of granular soils is strongly related to the grain size, thus numerous empirical correlations have been developed to estimate permeability using its grain size characteristics. In this study the empirical correlations proposed by Hazen (1911), Carrier (2003) and Chapuis (2004) are evaluated and compared to laboratory measurement results. Quaternary Danube soils are very typical in the Carpathian basin, thus their permeability is an important question in many geotechnical applications.

scholarly journals Performance investigation of a volute porous tongue of a turbocharger turbine

2020 ◽  
Vol 40 (1) ◽  
pp. 59-66
Author(s):  
Abderrahmane Chachoua ◽  
Mohamed Kamal Hamidou ◽  
Mohammed Hamel
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Gas Turbines ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Recirculation Flow ◽  
Recirculating Flow ◽  
Show Evidence ◽  
The Right

The design for better performance of the spiral housing volute used commonly in radial and mixed inflow gas turbines is of prime importance as it affects the machine stage at both design and off design conditions. The tongue of the scroll divides the flow into two streams, and represents a severe source of disturbances, in terms of thermodynamic parameter uniformity, maximum kinetic energy, the right angle of attack to the rotor and minimum losses. Besides, the volute suffers an undesirable effect due to the recirculating mass flow rate in near bottom vicinity of the tongue. The present project is an attempt to design a tongue fitted with cylindrical holes traversing normal to the stream wise direction, where on account of the large pressure difference between the top and the bottom sides of the tongue will force the recirculating flow to go through the rotor inlet. This possibility with its limitations has not yet been explored. A numerical simulation is performed which might provide our suitable objectives. To achieve this goal the ANSYS code is used to build the geometry, generate the mesh, and to simulate the flow by solving numerically the averaged Navier Stokes equations. Apparently, the numerical results show evidence of favorable impact in using porous tongue. The realization of a contact between the main and recirculation flow by drilled holes on the tongue surface leads to a flow field uniformity, a reduction in the magnitude of the loss coefficient, and a 20 % reduction in the recirculating mass flow rate.

Simulation of Multistage Compressor at Off-Design Conditions

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Feng Wang ◽  
Mauro Carnevale ◽  
Luca di Mare ◽  
Simon Gallimore
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Eddy Viscosity ◽  
Turbulence Models ◽  
Viscosity Model ◽  
Eddy Viscosity Model ◽  
Pressure Profiles ◽  
Multistage Compressor ◽  
Stage Matching ◽  
The Right

Computational fluid dynamics (CFD) has been widely used for compressor design, yet the prediction of performance and stage matching for multistage, high-speed machines remains challenging. This paper presents the authors' effort to improve the reliability of CFD in multistage compressor simulations. The endwall features (e.g., blade filet and shape of the platform edge) are meshed with minimal approximations. Turbulence models with linear and nonlinear eddy viscosity models are assessed. The nonlinear eddy viscosity model predicts a higher production of turbulent kinetic energy in the passages, especially close to the endwall region. This results in a more accurate prediction of the choked mass flow and the shape of total pressure profiles close to the hub. The nonlinear viscosity model generally shows an improvement on its linear counterparts based on the comparisons with the rig data. For geometrical details, truncated filet leads to thicker boundary layer on the filet and reduced mass flow and efficiency. Shroud cavities are found to be essential to predict the right blockage and the flow details close to the hub. At the part speed, the computations without the shroud cavities fail to predict the major flow features in the passage, and this leads to inaccurate predictions of mass flow and shapes of the compressor characteristic. The paper demonstrates that an accurate representation of the endwall geometry and an effective turbulence model, together with a good quality and sufficiently refined grid, result in a credible prediction of compressor matching and performance with steady-state mixing planes.

The mechanism of water absorption by roots I. Preliminary studies on the effects of hydrostatic pressure gradients

1957 ◽  
Vol 147 (928) ◽  
pp. 367-380 ◽  
Keyword(s):  
Hydrostatic Pressure ◽  
Pressure Gradient ◽  
Mass Flow ◽  
Osmotic Potential ◽  
Permeability Coefficient ◽  
External Medium ◽  
External Pressure ◽  
Pressure Gradients ◽  
Unit Change ◽  
Direct Technique

During transpiration the hydrostatic tension which develops in the xylem conducting elements of the root draws water from the soil through the intervening tissues of the cortex, etc. It is uncertain whether this movement is entirely diffusional or in part a mass flow. To detect any such mass flow tomato plants grown in water culture were decapitated and placed in a canister through the lid of which the cut stem protruded and in which the pressure on the culture medium could be raised. The resulting rate of exudation (flux) was measured, and compared with the flux caused by an equivalent difference in osmotic potential obtained by measuring the ∆ f. p. of the medium and sap exuded. If these values of flux were equal, movement was by diffusion alone, but if pressure caused a greater flux, an additional mass flow was indicated. Preliminary experiments indicated a much greater flux in response to differences of pressure than osmotic potential, but accurate assessment of the effect was precluded by difficulties inherent in this straightforward approach. A less direct technique was therefore devised; the change in flux caused by changing the osmotic potential of the external medium (the hydrostatic pressure being maintained constant) was compared with the change in flux caused by changing the external pressure (the osmotic potential of the external medium being kept constant). The changes in flux were measured in such a way as to minimize changes in the osmotic potential in the xylem and in resistances to diffusion or mass flow respectively. In this way the change in flux per unit change in osmotic potential difference across the cortex (osmotic permeability coefficient, k 0 ) and the change in flux per unit change in pressure difference across the cortex (pressure permeability coefficient, k p ) could be compared under the same pressure gradient and in addition the effects of pressure gradients on k 0 could be studied. Thus, the effects of a pressure gradient on the diffusional movement of water could be assessed, as well as any mass flow component of the flux detected and measured.

scholarly journals Combined Effects of Thermotherapy along with Scapular Muscles Strenghtening in Cervical Radiculopathy: A Case Report

2021 ◽  
Author(s):  
Shaikh Mohammad Aeraj ◽  
Tajuddin Chitapure
Keyword(s):  
Spinous Process ◽  
Cervical Radiculopathy ◽  
Nerve Roots ◽  
Cervical Nerve ◽  
Future Studies ◽  
Sensorimotor Deficits ◽  
Forward Flexion ◽  
Initial Hypothesis ◽  
The Right ◽  
Tissue Tension

Cervical radiculopathy is a syndrome in which the patient complains of pain along with sensorimotor deficits. This syndrome commonly develops due to compression of the cervical nerve roots. This report describes the case of 52-year-old histopathology laboratory technician who developed cervical radiculopathy due to prolonged cervical forward flexion while working on his table. The patient also complained of pain on the right scapular border. Radiographic analysis showed cervical spondylosis having osteophyte formation on spinous process of C2, C3, C4, C5 and C6 vertebras. Neural tissue tension test was positive for median nerve. He was treated consecutively with strengthening for shoulder abductors, shoulder adductors, scapula elevators and scapular protractors along with thermotherapy. His right medial border scapular pain and symptoms of cervical radiculopathy decreased in severity after the seventh day of treatment. Although the authors cannot suggest a cause-and effect relationship, this report allows for initial hypothesis development that thermotherapy approach may have clinical merit. Future studies in the form of well-designed, randomised clinical trials should be performed to evaluate the effectiveness of this approach in patients with cervical radiculopathy

scholarly journals Analysis of thermal flow in waterwall tubes of the combustion chamber depending on the fluid parameters

2019 ◽  
Vol 23 (Suppl. 4) ◽  
pp. 1333-1344 ◽  
Author(s):  
Marek Majdak ◽  
Slawomir Gradziel
Keyword(s):  
Combustion Chamber ◽  
Mass Flow ◽  
Power Plants ◽  
Thermal Flux ◽  
Momentum Conservation ◽  
Operating Conditions ◽  
Working Fluid ◽  
Difference Quotients ◽  
The Right ◽  
Fluid Parameters

The article presents the method of determining the temperature distribution in waterwall tubes of the combustion chamber. To simulate the operating conditions of waterwall tubes have been selected the model with distributed parameters, which is based on the solution of equations of the energy, mass and momentum conservation laws. The purpose of the calculations is determining the enthalpy, mass-flow and pressure of the working fluid flowing inside the tubes. The balance equations have been transformed into a form in which spatial derivatives are on the left, and the right side contains time derivatives. Then the time derivatives were replaced with backward difference quotients, and the obtained system of differential equations was solved by the Runge-Kutta method. The analysis takes into account the variability of fluid parameters depending on the mass-flow at the inlet of the tube and heat flux on the surface of the tube. The analysis of fluid parameters was carried out based on operating parameters occurring in one of the Polish supercritical power plants. Then it was compared with characteristics for systems operating at increased or reduced thermal flux on the walls of the furnace or systems operating at increased or reduced mass-flow of the working fluid at the inlet to the waterwall tube.

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